In recent years, a power generating element which can generate electric power by utilizing a variation of magnetic permeability of a magnetostrictive rod formed of a magnetostrictive material has been developed (for example, see patent document 1).
For example, a power generating unit (power generating element) described in the patent document 1 includes a rod-like super magnetostrictive member (magnetostrictive rod), two permanent magnets respectively attached to both end portions of the super magnetostrictive member and a coil wound around the super magnetostrictive member. When the super magnetostrictive member is deformed (or compressed) in an axial direction thereof or deformed (or bent) in a direction perpendicular to the axial direction thereof, that is, when expansion and contraction occur in the super magnetostrictive member, magnetic permeability of the super magnetostrictive member varies. By utilizing the variation of the magnetic permeability of the super magnetostrictive member, it is possible to vary a magnetic field around the super magnetostrictive member, and thereby generating a voltage in the coil.
Since the power generating unit having such a configuration generates electric power by utilizing the expansion and the contraction of the super magnetostrictive member, strong connecting forces between the super magnetostrictive member and each of the permanent magnets (that is, strong connecting forces between the super magnetostrictive member and other components) are required. In particular, a strong connecting force is especially required when the super magnetostrictive member is expanded. However, it is hard to say that the power generating unit described in the patent document 1 has sufficient connecting forces between these components.